Add Documentation for $Context.(Field Name)

[LukePercy]

When viewing the formatting help for a Notify Email there is a series of Calls you can make and one in particular, $Context.(field name)

Can we get documentation on what these field names are, or some that would generally be used in notify emails.

For example a Page Name/Title etc. This would be particularly useful in Summaries to notify what pages need review before publishing.

[phptek]

From what I can tell in the logic, if you knew the standard DB fields available on "Page", and "Member" any of these would work so fairly straightforward to update the docs and double-check that this is actually the case.

[phptek]

@LukePercy can you check that what you get in the way of comments in the NotifyUsers action in the module now, is sufficient?